Measuring the temperature of a direct heated apparatus with a thermocouple is desirable for various applications. U.S. Patent Application Publication No. 2008/0175304 to Adelsberg et al. (hereinafter the “Adelsberg publication”) discloses a thermocouple circuit that exhibits reduced levels of thermocouple drift. The Adelsberg publication discloses the thermocouple including first and second tab elements that are spaced apart from another.
FIG. 1 illustrates a schematic view of a conventional arrangement of a thermocouple 101 including first and second tab elements 103, 105 attached to an electrically conductive substrate 107. The electrically conductive substrate 107 is operably connected to a direct heating apparatus 109 configured to heat the substrate with an electrical current flowing through the substrate. As shown, the tab elements 103, 105 are spaced apart from one another along a horizontal axis 111 that is parallel to a direction 113 of the electrical current flowing through the substrate.
As described in the Adelsberg publication, the spaced apart tabs are useful to reduce levels of thermocouple drift. However, spacing the tab elements as shown in FIG. 1 may exhibit excess EMF noise due, at least in part, to the flow of an electric current in the direction 113 along the axis 111 of the spaced apart tabs 103, 105. The thermocouple typically generates EMF signal that varies with temperature. The EMF signal may cause excess signal noise that interferes with the operation of the thermocouple. For example, at 1650° C., a conventional type B thermocouple may generate an 11.848 mVDC EMF. At the same temperature, a conventional type S thermocouple may generate a 17.366 mVDC EMF. By spacing tab elements of a thermocouple in the orientation shown in FIG. 1, additional excess EMF signal noise (e.g., an additional 64.8 mVDC) may be generated on top of the EMF signal noise that the type B and type S thermocouples normally produce. This excess signal noise may produce a 4° to 5° C. signal noise. The 4° to 5° C. signal noise may lead to inaccurate temperature readings of the substrate, thereby complicating the use of the thermocouple in a monitoring or control capacity.